Means for recording and reproducing sound



Patented Nov. 26, 1929 I v UNITED STATES PATENT OFFICE,

ALFRED -AU'BYN' LINSELL, OI BBENTWOOD,,ZENGLAND, ASS IGNOR EEO-RADIOCORPORA- TIOiN OF AMERICA, A CORPORATION OF DELAWARE I MEANS FORRECORDING AND BEP BODUCING SOUND Application filed. September 28, 1927,Serial No.

This invention relates to means for recordmg and/ or reproducing sound,and more particularly to means for recording sound upon gramophone andthe like records and/or reproducing sound therefrom.

According to this invention nieans for recording or reproducing soundcomprise a piezo-electri'c crystal, means for applying otential to orderiving potential from one or more of the faces of'the crystal, andmeans for applying force to or deriving force from one or more of thefaces of the crystal.

The piezo-electric. crystal may be employed in conjunction with aseparate stylus device, such as a steel point or a sapphire, butpreferablysuch stylus device is formed integral with the crystal.

In carrying out the invention for the reproduction of sound from agramophone or the like record, a suitably cutpiezo-electric crystal issubjected to a compressive, followed in certain cases by a tensile, ingin such a manner as to produce a corresponding contraction or extensionof the crystal in a plane containing any two of the principal axesthereof, the said forcebeing applied by and due to the movement of astylus, aflixed to the saidcrystal, and in conof a piezo-electriccrystal are the optical axis,

tact with, the sound trace of a phonograph or gramophone record. Theseprincipal axes the electrical axis, and the geometrical axis which isperpendicular to the optical and electrical axes.- The application offorce to the electric potential, derived from two opposite faces of thecrystal, either or both of which undergo the compression or tension. Itwill be seen that the electrical potential developed will correspondwith the sound trace on the record. This potential may be amplified inany known manner, converted into sound waves by means of a telephone, rother suitable instrument.

Similarly, in the case of recording, the sound waveslafter amplificationif desired are converted into corresponding electrical potentials, whichare applied toopposite faces of a suitably cut piezo-electrlc crystal,thereby causing a physical deformation of the crystal,

force, actcrystal results in the generation therein of an.

and finally,

andin Great Britain October 2, 1926.

which is utilized to cut a sound trace on a gramophone or phonographrecord.

In one form of construction the crystal is 'mounted in a holder orcarriage attached by a flexible coupling to an arm'positioned close tothe record and pivoted in such a manner as to allow the carriage tomove-across the record face following the course-of the sound trace. Theweight, and therefore the inertia, of the carriage is such, and isso'positioned, that it provides a substantially rigidholder for thecrystalin relation to the surface ofthe record, while at the same timethe flexible coupling prevents any unevenness in the movement ofthe-record table (due, for example, to eccentricity of mounting), fromaffecting the crystal. Y

Although any known type of stylus, such, for example, as a steel pointor sapphire, may be usedwith the piezo-electric crystal arrangementsherein described, it is preferred of the pyramid being the Two examplesof arrangements in accordance with the invention will now'be described.The first example relates to phonograph or pathephone reproduction.

From a piezolectric crystal such a quartz, I

a rectangular plate is. cut whose faces are parallel to the opticalaxis, the electrical axis, and a geometrical axis which is perpendicularto the optical, and electrical axes, respectively.

In the center of the face containing the electrical .and eometrical axesis affixed the stylus, or a ternatively, this face may be ground with aprojection shaped to act as the stylus. The crystal is mounted in acarriage so that the face carrying the stylus projects freely from it,and the opposite face bears on the body of the carriage. Two rectangularelectrodes are provided on the two faces containingthe optic andgeometric axes, and

- these electrodes may also assist in retaining the crystal in thecarriage. Other side members may also be provided for retaining thecrystal in position, if desired. The carriage is joined to a pivoted armby a rubber or similar flexible coupling, the weight of the carriagebeing suflicient to provide a substantially rigid holder for the crystalwith respect to the record. The crystalin its carriage is then mountedabove the record, with the stylus in contact with the sound trace in theusual manner. It will be clear, therefore, that the varying contour ofthe sound trace will cause the stylus to move in a direction parallel tothe optic axis, and this in its turn, since the carriage issubstantially rigid, due to its inertia, will tend to cause the crystalto expand in the direction of the electrical and accordance with theoriginal sound trace on reproduction.

the record. v

The second example refers to gramophone This is generally similar to theexample just described, but a different method of mounting the crystalis adopted, and the position of the stylus on the face of the crystal isalso altered. The reason for this alteration is due to the differencebetween the sound trace on a phonograph or pathephone and a gramophonerecord, the first producing an up and down movement of the stylus, whilethe second gives v a side to side movement. In other respects.

the procedure isas before. The'crystal is cut in a similar manner, andthe faces containing the optical and geometrical axes are again,

provi ed with electrodes, but thestylus, instead of being positioned inthe center of the face containing the electrical and geometrical axes,is now positioned at the center of one of parallel to the electricalaxis. The crystal with its carriage is then positionedabove thegramophone record with the side carrying the stylus in the center maklnga tangent with the circular groove of the sound trace, the stylus beingof course in contact with the said trace. The resultlng movement ofthestylus in one direction, due to the I sound trace, will therefore causethe whole or a part of the face containing the optical and. geometricalaxes to contract, while movement mthe other direction will cause it toexpand. This expansion and contraction will generate electricalpotential as before, which may be a lified as desired. I

is to be understood that the foregoing generated.

examples are by way of illustration onl and that other arrangements maybe adopted without departing from the scope of the invention. Forexample, the shape of the crystal has been described as rectangular butother shapes may be used, as, for instance, one in which two or more ofthe faces are triangular. Also the electrodes have. been de-.=

scribed as rectangular, butagain other shapes may beused, as, forinstance, triangular, and the said electrodes need not be of the sameshape as the faces of the crystal on which they are positioned. Again,the relative position of the axes in relation to the carriage stylus andrecord may be interchanged an varied.

Further, if desired, the stylus in the case of the gramophone ma beplaced at any other desired position on t e face of the crystal, and notonly on one side as hereinbefore described.

In one such modified arrangement the potential generated on one face ofthe cr stal only is utilized, and another electro e is positioned nearto, but insulated from, this face, this second electrode serving as thesecond pole, between which and the electrode on the crystal face, thevarying potential is The invention is illustrated in the accompanyingdrawings.

Referring to Figures 1 and 2, which show in front and side elevationrespectively a piezo-electric crystal cut to a form suitable forphonograph recording and reproduction,-

l is the main body of the crystal and4 a part of the said crystal cut toform a point adapted to form, in effect, a stylus. The edge A B isparallel to the optic axis of the crystal, the edge A D parallel to thegeometric axis, and the ed e A E parallel to the electric .axis thereoThe part 4 may be cut to any desired degree of sharpness.

Figures 3 and 4 show in front and side elevation respectively a slightlymodified form of crystal in which the part 4 is cut more abruptly.

In the modification shown in front and side elevation respectively inFigures 5 and 6, the part 4, formed in the above describedconstr'uctions integrally. with the main body of the crystal, isreplaced by a steel stylus needle 4 of known form, clamped in atroughshaped member 2 by means ofa set screw 3, the said troughretaining the crystal 1.

Figures 7 and 8 show in front and side elevation respectively a form ofcrystal suit able for use in gramophone reproduction.

This form is generally similar to the forms shown in Figures 1, 2, 3'and4, except that the part 4, which is formed integrally with the main bodyof the crystal, is displaced. towards the face A --H instead of beinglocated substantially at the center of the face H. v

When such a crystal is mounted perpendicular to the surface of agramophone record, with the part Pin contact with the trace thereof'andthe face AB C D at right angles to the said trace, the said part 4 willexperience forces in a direction aralleh to the edge D C. Therefore,when a to move the .part 4 to the left, the area Y ofthe crystal to theleft of the line X X will experience compression, while the area Z tothe right thereof will experience tension, a reversal of these forcestaking place when a force tends to move the part 4 to-the right. It willbe clear that under the influence of the forces, electrical potentialswill be generated in,the areas to left and right of the" line X X, Iftherefore a pair of connected "electrodes be placed in contact with area-on the front of .the crystal and area Z on the back thereof, and asecond pair of connected electrodes insulated from the first pairbe'pla'ced in contactwith area Z on the front of the crystal and area Yon the back, thereof, equal potentials of opposite sign may be collectedfrom the pairs of electrodes. These potentials may be utilized toactuate any known form of'electrical sound translating device, such as,a telephone.

In a modification (illustrated in front and side elevation respectivelyin Figures 7 A and 8A) of the'last described arrangement, the stylus isformed as an abrupt pomt similar 3 to that shown in Figures 3 and'4, but-d1splaced towards the face A In this case a force, tending tomove thestylus 4 to the left, will cause substantially the whole of the face-A BC D to undergo tension, wh le a force, tending to move .the stylus totheright, will cause a corresponding compression over substantially thewhole face this modification, therefore, trodes are required coverin thewhole of the face A B Cv responding rear face. p

Figures 9, 10 and 11 show in front and slde elevation and planrespectively a convenient form of carriage and electrode arrangement.This arrangement, which is adapted tecarry any of the forms of crystalshown in F gures 1 to 6, comprises a metal box consisting of two halvesand 6, insulated from one another by a member 9 (or by an air spacerendering the said member 9 unnecessary) and carrying between them thecrystal 1 which is held in position by means of screws passing throughthe said halves but insulated therefrom by ebonite or the like bushings8. I In this way the box halves 5 and 6 serve the double function ofretaining tlg crystal and serving as electrodes in contact with thecrystal facescontaining the optic and geometric axes. If desired, thebox halves 5 and 6 may substantially and the cor- 05 be insulated fromthe crystal faces containorce tends Y tion,

A B C D. With only two elecing the electric and geometric axes by narrowstrips of mica, ebonite or the like.

It will be seen that with the arrangement shown-in Figures 9,10 and 11,if the crystal in its mounting be located above a phonograph record,with the part 4 in contact with the sound trace thereon, the said partbe subjected to varying degrees of pressure in a direction perpendicularto the face of the record,and this pressure will be imparted to the bodyof the crystal, tending to cause the crystal to expand in a directionperpendicular to the face A B C 1),. Corresponding electrical potentialswill therefore be generated on those faces which are in contact with theelectrodes 5 and 6, and these potentials may be applied preferably afteramplificato actuate any known form of electrical sound translatingdevice, such as a telephone.

Figuresv 12,, 13 and 14 show in front and will 1 side elevation and planrespectively a conveni'ent form of carriage and electrode arrangement,suitable for use in gramophone recording or reproduction, with a crystalsuch as that shown in Figures 7 and 8. In this arrangement the carriagecomprises four members' 5, 6, 5 and 6, clamped together to retain thecrystal by means of screws 7 insulated by bushings 8. 9, 9, 9" areinsulating members which may, however, be dispensed with if the members,5, 6, 5, 6, are so shaped and are of such size that when in positionabout a crystal there'is a suflicient air spacebetween their edges toprovide-the required insulation.

"Figure 15 shows in diagrammatic form a suita 1e amplifier arrangementfor use with any'of the foregoing crystal arrangements.

Referring to this figure, 10 is a thermionic valve whose grid andcathode are connected across the potential generating electrodes.

For example, with the arrangement shown in Figures 9 to 11, the grid andcathode would be connected across electrodes 5 and 6, while in thearrangement shown in Figures 12 to '14, the said grid and cathode wouldbe connected across the pairs of electrodes 5, 6' and 5, 6; '11 is animpedance connected in series with a bias battery 12, between the saidid and filament. 13, 14 are the primary an secondary of a transformer,the secondary of which is adapted to actuate a telephone, loud speakeror the like .(not shown) Having now particulaiily described andascertained the nature of .my said invention and in whatmanner the sameis to be performed, I declare that what I claim is:

1. A reversible'electrical reproducer comelectro es connected to twoopposite faces ofsaid body portion.

.2. In an electrical reproducer adapted to Joe rising a piezo electriccrystal section, said generate electrical impulses in accordance withgroove variations in a record device, a stylus shaped to fit saidgrooves, said stylus being formed of a 'piezo electric material.

3. In an electrical reproducer adapted to generate electrical impulsesin accordance with groove variations in a record device, a piezoelectric body adapted to transform mechanical vibrations into electricaloscillations or electrical oscillationsinto mechanical vibrations, and astylus integrallyformed on said body and of the same material.

4. In an electrical reproducer adapted to generate elcctricalimpulses inaccordance with groove variations'in a piezo electric crystal sectionorm electrical oscillations vibrations and mechanical vibrations intoelectrical oscillations, said crystal comprising abody portion, a stylusintegral with and projecting from said body portion, and pair ofelectrodes connected to said body portion.

5. In an electrical ,reproducer adapted to generate electrical,impulses" in accordance with groove variations in a record device, apiezo electric crystal section comprising a body portion and a stylusintegrally formed with said body portion and of the same material.

6. In an electrical reproducer adapted to generate electrical impulsesin accordance adapted to transwith groove variations in a record device,a.

piezo electric crystal parallelopiped and a pyramidal extensionintegrally formed at one side of said parallelopiped, said extensionbeing shaped to fit into said groove variations. 1

ALFRED AUBYN LINSELL.

record device, a-

into mechanical

